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Typically, denitrification occurs in anoxic environments, where the concentration of dissolved and freely available oxygen is depleted. In these areas, nitrate (NO 3 −) or nitrite (NO 2 −) can be used as a substitute terminal electron acceptor instead of oxygen (O 2), a more energetically favourable electron acceptor. Terminal electron ...
In wastewater treatment, the absence of oxygen alone is indicated anoxic while the term anaerobic is used to indicate the absence of any common electron acceptor such as nitrate, sulfate or oxygen. When oxygen is depleted in a basin, bacteria first turn to the second-best electron acceptor, which in sea water, is nitrate.
Since denitrifying bacteria are heterotrophic, an organic carbon source is supplied to the bacteria in an anoxic basin. With no available oxygen, denitrifying bacteria use the redox of nitrate to oxidize the carbon. This leads to the creation of nitrogen gas from nitrate, which then bubbles up out of the wastewater. [16]
N 2 fixation has been found in some anoxic systems, generally associated with sulfate reducers or oxidizers. [8] However, heterotrophic denitrification is a more dominant process under anoxic conditions. Denitrification is the reduction of NO 3 − and NO 2 − to the gaseous form of nitrogen (N 2), including the greenhouse gas nitrous oxide (N ...
Nitrate levels also contribute to eutrophication, a process in which large algal blooms reduce oxygen levels in bodies of water and lead to death in oxygen-consuming creatures due to anoxia. Nitrification is also thought to contribute to the formation of photochemical smog, ground-level ozone, acid rain , changes in species diversity , and ...
In severe anoxic conditions, microbial life may experience dramatic shifts in community identity as well, resulting in an increased abundance of anaerobic organisms as aerobic microbes decrease in number and switch energy sources for oxidation such as nitrate, sulfate, or iron reduction.